This module allows logs to be stored in Hadoop HDFS using the WebHDFS protocol.
The om_webhdfs module accepts the following directives in addition to the common module directives. The File and URL directives are required.
This mandatory directive specifies the name of the destination file. It must be a string type expression. If the expression in the File directive is not a constant string (it contains functions, field names, or operators), it will be evaluated before each request is dispatched to the WebHDFS REST endpoint (and after the Exec is evaluated). Note that the filename must be quoted to be a valid string literal, unlike in other directives which take a filename argument.
This mandatory directive specifies the URL of the WebHDFS REST endpoint where the module should POST the event data. The module operates in plain HTTP or HTTPS mode depending on the URL provided, and connects to the hostname specified in the URL. If the port number is not explicitly indicated in the URL, it defaults to port 80 for HTTP and port 443 for HTTPS.
The module will send the data to the endpoint defined in URL after this amount of time in seconds, unless FlushLimit is reached first. This defaults to 5 seconds.
When the number of events in the output buffer reaches the value specified by this directive, the module will send the data to the endpoint defined in URL. This defaults to 500 events. The FlushInterval may trigger sending the write request before this limit is reached if the log volume is low to ensure that data is sent promptly.
This boolean directive specifies whether the connection should be allowed with an expired certificate. If set to
TRUE, the connection will be allowed even if the remote server presents an expired certificate. The default is
FALSE: the remote server must present a certificate that is not expired.
This boolean directive specifies that the connection should be allowed regardless of the certificate verification results. If set to
TRUE, the connection will be allowed with any unexpired certificate provided by a server. The default value is
FALSE: the remote server must present a trusted certificate.
This directive specifies a path to a directory containing certificate authority (CA) certificates. These certificates will be used to verify the certificate presented by the remote server. The certificate files must be named using the OpenSSL hashed format, i.e. the hash of the certificate followed by .0, .1 etc. To find the hash of a certificate using OpenSSL:
$ openssl x509 -hash -noout -in ca.crt
For example if the certificate hash is
e2f14e4a, then the certificate filename should be
e2f14e4a.0. If there is another certificate with the same hash then it should be named
e2f14e4a.1and so on.
A remote server’s self-signed certificate (which is not signed by a CA) can also be trusted by including a copy of the certificate in this directory.
This specifies the path of the certificate authority (CA) certificate that will be used to verify the certificate presented by the remote server. A remote server’s self-signed certificate (which is not signed by a CA) can be trusted by specifying the remote server certificate itself. In case of certificates signed by an intermediate CA, the certificate specified must contain the complete certificate chain (certificate bundle).
This optional directive specifies the thumbprint of the certificate authority (CA) certificate that will be used to verify the certificate presented by the remote server. The hexadecimal fingerprint string can be copied from Windows Certificate Manager (certmgr.msc). Whitespaces are automatically removed. The certificate must be added to a Windows certificate store that is accessible by NXLog. This directive is only supported on Windows and is mutually exclusive with the HTTPSCADir and HTTPSCAFile directives.
This optional boolean directive, when set to
TRUE, enables the loading of all available Windows certificates into NXLog, for use during remote certificate verification. Any required certificates must be added to a Windows certificate store that NXLog can access. This directive is mutually exclusive with the HTTPSCAThumbprint, HTTPSCADir and HTTPSCAFile directives.
This specifies the path of the certificate file to be used for the HTTPS handshake.
This specifies the path of the private key file that was used to generate the certificate specified by the HTTPSCertFile directive. This is used for the HTTPS handshake.
This optional directive specifies the thumbprint of the certificate that will be presented to the remote server during the HTTPS handshake. The hexadecimal fingerprint string can be copied from Windows Certificate Manager (certmgr.msc). Whitespaces are automatically removed. The certificate must be imported to the
Local Computer\Personalcertificate store in PFX format for NXLog to find it. To create a PFX file from the certificate and private key using OpenSSL:
$ openssl pkcs12 -export -out server.pfx -inkey server.key -in server.pem
This directive is only supported on Windows and is mutually exclusive with the HTTPSCertFile and HTTPSCertKeyFile directives.
This directive specifies a path to a directory containing certificate revocation list (CRL) files. These CRL files will be used to check for certificates that were revoked and should no longer be accepted. The files must be named using the OpenSSL hashed format, i.e. the hash of the issuer followed by .r0, .r1 etc. To find the hash of the issuer of a CRL file using OpenSSL:
$ openssl crl -hash -noout -in crl.pem
For example if the hash is
e2f14e4a, then the filename should be
e2f14e4a.r0. If there is another file with the same hash then it should be named
e2f14e4a.r1and so on.
This specifies the path of the certificate revocation list (CRL) which will be used to check for certificates that have been revoked and should no longer be accepted. Example to generate a CRL file using OpenSSL:
$ openssl ca -gencrl -out crl.pem
This optional directive specifies file with dh-parameters for Diffie-Hellman key exchange. These parameters can be generated with dhparam(1ssl). If no directive is specified, default parameters will be used. See OpenSSL Wiki for further details.
This directive specifies the passphrase of the private key specified by the HTTPSCertKeyFile directive. A passphrase is required when the private key is encrypted. Example to generate a private key with Triple DES encryption using OpenSSL:
$ openssl genrsa -des3 -out server.key 2048
This directive is not needed for passwordless private keys.
This optional directive can be used to set the permitted SSL cipher list, overriding the default. Use the format described in the ciphers(1ssl) man page. For example specify
RSA:!COMPLEMENTOFALLto include all ciphers with RSA authentication but leave out ciphers without encryption.
|If RSA or DSA ciphers with Diffie-Hellman key exchange are used, DHFile can be set for specifying custom dh-parameters.|
This optional directive can be used to set the permitted cipher list for TLSv1.3. Use the same format as in the HTTPSSSLCipher directive. Refer to the OpenSSL documentation for a list of valid TLS v1.3 cipher suites. The default value is:
This boolean directive allows you to enable data compression when sending data over the network. The compression mechanism is based on the zlib compression library. If the directive is not specified, it defaults to
FALSE: compression is disabled.
Some Linux packages (for example, Debian) use the OpenSSL library provided by the OS and may not support the zlib compression mechanism. The module will emit a warning on startup if the compression support is missing. The generic deb/rpm packages are bundled with a zlib-enabled libssl library.
This directive can be used to set the allowed SSL/TLS protocol(s). It takes a comma-separated list of values which can be any of the following:
TLSv1.3. By default, the
TLSv1.3protocols are allowed. Note that the OpenSSL library shipped by Linux distributions may not support
SSLv3, and these will not work even if enabled with this directive.
This configuration option can be used to specify additional HTTP Query Parameters such as BlockSize. This option may be used to define more than one parameter:
QueryParam blocksize 42 QueryParam destination /foo
This optional directive sets the reconnect interval in seconds. If it is set, the module attempts to reconnect in every defined second. If it is not set, the reconnect interval will start at 1 second and doubles with every attempt. If the duration of the successful connection is greater than the current reconnect interval, then the reconnect interval will be reset to 1 sec.
The Reconnect directive must be used with caution. If it is used on multiple systems, it can send reconnect requests simultaneously to the same destination, potentially overloading the destination system. It may also cause NXLog to use unusually high system resources or cause NXLog to become unresponsive.
The following procedures are exported by om_webhdfs.
Force a reconnection. This can be used from a Schedule block to periodically reconnect to the server.
The reconnect() procedure must be used with caution.
If configured, it can attempt to reconnect after every event sent, potentially overloading the destination system.
This example output module instance forwards messages to the specified URL and file using the WebHDFS protocol.
<Output hdfs> Module om_webhdfs URL http://hdfsserver.domain.com/ File "myfile" QueryParam blocksize 42 QueryParam destination /foo </Output>